Sulfonic Acid-functionalized Mesoporous Silica Research Articles

Sustainable Sulfonic Acid Functionalized Tubular Shape Mesoporous Silica as a Heterogeneous Catalyst for Selective Unsymmetrical Friedel-Crafts Alkylation in One Pot.

The development of general and more sustainable heterogeneous catalytic processes for Friedel-Crafts (FC) alkylation reactions is a key objective of interest for the synthesis of pharmaceuticals and commodity chemicals. Sustainable heterogeneous catalysis for the typical FC alkylation of an easily accessible carbonyl electrophile and arenes or with two different arene nucleophiles in one-pot is a prime challenge. Herein, we present a resolution to these issues through the design and utilization of a mesoporous silica catalyst that has been functionalized with sulfonic acid. For the synthesis of sulfonic acid-functionalized mesoporous silica (MSN-SO3H), thiol-functionalized mesoporous silica was first synthesized by the co-condensation method, followed by oxidation of the thiol functionality to the sulfonic acid group. Sulfonation of mesoporous silica was confirmed by 13C CP MAS NMR spectroscopy. Further, the devised heterogeneous catalysis using MSN-SO3H has been successfully employed in the construction of diverse polyalkanes including various bioactive molecules, viz arundine, tatarinoid-C, and late-stage functionalization of natural products like menthol and Eugenol. Further, we have utilized this sustainable technique to facilitate the formation of unsymmetrical C-S bonds in a one-pot fashion. In addition, the catalyst was successfully recovered and recycled for eight cycles, demonstrating the high sustainability and cost-effectiveness of this protocol for both academic and industrial applications.

Sulfonic acid-functionalized mesoporous silica catalyst with different morphology for biodiesel production

Sulfonic acid-functionalized mesoporous silica catalyst with different morphology for biodiesel production

Acetalization of glycerol with hexanal in the presence of SBA-15 with sulfonic acid groups

Acetalization of glycerol with hexanal was studied over sulfonic acid-functionalized mesoporous silica (SBA-15), at 70 ºC. The product obtained were (2-pentyl-1,3-dioxolan-4-yl)methanol and 2-pentyl-1,3-dioxan-5-ol. Materials with different amounts of sulfonic acid groups were prepared. The support functionalization was achieved by the introduction of 3-(mercaptopropyl)trimethoxysilane onto the surface of these materials by grafting technique. The [SO3H]-SBA-15 catalysts were characterized by nitrogen adsorption at 77 K, X-ray diffraction, SEM and titrations. All the catalysts were active in the studied reaction being the [SO3H]3-SBA-15 the best one. It was observed that the reaction rate increase with the amount of sulfonic acid groups on SBA-15 until a maximum. With high amounts of sulfonic groups, a decrease of activity is observed. Good values of selectivity to (2-pentyl-1,3-dioxolan-4-yl)methanol were obtained with mesoporous silicas anchored sulfonic acid groups. Catalytic stability of the [SO3H]3-SBA-15 was evaluated by performing consecutive batch runs with the same catalyst sample. The material showed a good catalytic stabilization.

Catalytic Performance of SBA-15-Supported Poly (Styrenesulfonic Acid) in the Esterification of Acetic Acid with n-Heptanol

A polystyrene sulfonic acid-functionalized mesoporous silica (SBA-15-PSSA) catalyst was synthesized via an established multistep route, employing 2-bromo-2-methylpropionyl bromide as initiator of atom transfer radical polymerization. Fourier-transform infrared spectroscopy, thermogravimetric/differential thermal, Brunauer–Emmett–Teller, and transmission electron microscopy analyses revealed outstanding structural characteristics of the catalyst, including highly ordered mesopores, high surface area (726 m2/g), and adequate estimated concentrations of active sites (0.70 mmol H+/g). SBA-15-PSSA’s catalytic performance was evaluated in the esterification of acetic acid and n-heptanol as a model system at various temperatures (50–110 °C), catalyst loads (0.1–0.3 g), and reaction times (0–160 min). The conversion percentage of acetic acid was found to increase with the temperature, catalyst load, and reaction time. Furthermore, results indicated a fast conversion in the first 20 min of the reaction, with remarkable conversion values at 110 °C, reaching 86%, 94%, and 97% when the catalyst load was 0.1, 0.2, and 0.3 g, respectively; notably, at this temperature, 100% conversation was achieved after 60 min. At 110 °C, the reaction conducted in the presence of 0.3 g of catalyst displayed more than 6.4 times the efficiency of the uncatalyzed reaction. Such activity is explained by the concomitant presence in the polymer of strong sulfonic acid moieties and a relatively high hydrophobic surface, with adequate numbers of active sites for ester production.

One-Pot Synthesis of Spiro[chromeno[2,3-c]pyrazole-4,3′-indoline]-diones Using Sulfonic Acid Functionalized Nanoporous Silica SBA-Pr-SO3H and Study of Their Antimicrobial Properties

ABSTRACTA novel and clean one-pot synthesis of spiro[chromeno[2,3-c]pyrazole-4,3′-indoline]-2′,5(6H)-diones via cyclocondensation reaction of isatins, 1,3-cyclohexadiones, and pyrazolone in aqueous media using SBA-Pr-SO3H (sulfonic acid-functionalized mesoporous silica) as an efficient heterogeneous solid acid catalyst was reported. The antimicrobial activities of synthesized compounds have been tested.

Efficient enrichment of glycopeptides with sulfonic acid-functionalized mesoporous silica

This work presents an efficient and selective enrichment method for glycoprotein/glycopeptides with sulfonic acid-functionalized mesoporous silica (SBA-15-SO3H), which is synthesized via simple oxidation of -SH groups with H2O2. The functionalized SBA-15 shows large surface area and accessible pores, and can selectively adsorb glycopeptides via hydrogen bond and hydrophilic interaction. Upon the selective enrichment prior to the mass spectrometric (MS) analysis, the signals of glycopeptides are significantly enhanced, which leads to the identifiable signals of 21 glycopeptides from the digest of HRP, 16 glycopeptides from the digest of human IgG, and 16 glycopeptides from the digest of chicken avidin. The SBA-15-SO3H gives significant selectivity for glycopeptides even at a low molar ratio of glycopeptides to nonglycopeptides with an enrichment time of 15min. Therefore, this work provides a powerful material for selective enrichment and identification of low abundant glycopeptides in glycoproteomic analysis.

Efficient synthesis of 3,3-di(indolyl)oxindoles catalyzed by sulfonic acid-functionalized mesoporous silica nanoparticles (SAMSNs) in aqueous media

An efficient protocol has been developed for the aqueous-mediated synthesis of 3,3-di(indolyl)oxindole derivatives via the electrophilic substitution reaction of indoles with various isatins using sulfonic acid-functionalized mesoporous silica nanoparticles (SAMSNs) as a recoverable heterogeneous acid catalyst. This catalyst can be reused several times without significant loss of activity.

Sulfonic acid-functionalized mesoporous silica nanoparticles (SAMSNs): a recoverable heterogeneous acid catalyst for green synthesis of dicoumarols

Sulfonic acid-functionalized mesoporous silica nanoparticles (SAMSNs) have been used as a highly efficient and recoverable heterogeneous acid catalyst for green synthesis of dicoumarols by reaction of different aldehydes with 4-hydroxycoumarin in aqueous media. High to excellent yields were obtained. This mesoporous catalyst is readily recovered and can be reused at least six times without significant loss of its catalytic activity.

Selective conversion of cellulose into bulk chemicals over Brønsted acid-promoted ruthenium catalyst: one-pot vs. sequential process

Acid hydrolysis and hydrogenation/hydrogenolysis reactions can be combined for catalytic conversion of cellulose into renewable biorefinery feedstocks by using two heterogeneous catalysts: sulfonic acid (–SO3H) functionalized mesoporous silica (MCM-41) and Ru/C. The combination is suitable for a one-pot tandem process to convert cellulose into alkanediols (mainly propylene glycol and ethylene glycol), yet deactivation of the sulfonic acid (–SO3H) functionalized mesoporous silica occurred rapidly after only one reaction cycle because of an irreversible change in the mesoporous structure and loss of acid groups. However, much better selectivity of hexitol or γ-valerolactone (GVL) can be obtained in a sequential tandem process by hydrogenating the hydrolysis products, glucose and levulinic acid (LA). A similar irreversible deactivation of acid catalyst also occurred when it involved the hydrogenolysis of glucose into alkanediols. When the sulfonic acid-functionalized mesoporous silica is filtered, and the hydrolysis products of cellulose are directly used in the hydrogenation reaction without further purification, a better selectivity and stability of hexitol production can be obtained. Under such conditions, the lifetime of the catalyst system can be significantly extended, up to 6 times the original durability of the acid-functionalized silica.

Mechanism of acetic acid esterification over sulfonic acid-functionalized mesoporous silica

The kinetics of acetic acid esterification with methanol using a propylsulfonic acid-functionalized SBA-15 catalyst were investigated. To determine whether a different mechanism was applicable for heterogeneous or homogeneous catalyzed esterification, propane sulfonic acid was also examined as this homogeneous acid has the same structure as the functional groups tethered onto SBA-15. In isothermal experiments at 323K, the apparent reaction orders using the heterogeneous catalyst were determined to be 0.72 for methanol and 0.87 for acetic acid. Reactant adsorption studies showed that pre-adsorption of acetic acid hindered the reaction rate, while pre-adsorption of methanol or acetic acid with methanol increased the reaction rate, indicating that acetic acid adsorbs more strongly than methanol over the heterogeneous acid catalyst. The experimental results demonstrated that acetic acid esterification with methanol followed a dual-site Langmuir–Hinshelwood type reaction mechanism, which required both the adsorption of acetic acid and methanol over propylsulfonic acid-functionalized SBA-15. In contrast, esterification reaction with the homogeneous catalyst followed an Eley–Rideal mechanism. The kinetic data were successfully fit with a model in which the surface reaction was the rate-limiting step.

Preparation and characterization for a new sulfonic acid-functionalized mesoporous silica stationary phase

A novel strategy for functionalized mesoporous silica used as chromatographic packing material is reported. Periodic mesoporous silica containing sulfonic acid bearing groups were synthesized using tetramethyloxysilicate (TMOS) and mercaptopropyltrimethoxysilane (MPTMS) as framework precursors under acidic conditions in the presence of Pluronic P123 as surfactant and cetyltrimethylammonium bromide (CTAB) as cosurfactant. Conversion of the mercaptopropyl groups into sulfonic acid moieties was achieved via oxidation using hydrogen peroxide. Wormhole mesostructure with high surface area (up to 718.6 m 2/g) and narrow pore size distribution (up to 4.0 nm) were obtained. The effect of the synthesized mesoporous silica microspheres as a HPLC packing material was examined.

Ion-Exchange Properties and Electrochemical Characterization of Quaternary Ammonium-Functionalized Silica Microspheres Obtained by the Surfactant Template Route

Porous silica spheres functionalized with quaternary ammonium groups have been prepared by co-condensation of N-((trimethoxysilyl)propyl)-N,N,N-trimethylammonium chloride (TMTMAC) and tetraethoxysilane (TEOS) in the presence of cetyltrimethylammonium as a template and ammonia as a catalyst. The physicochemical characteristics of the resulting ion exchangers have been analyzed by various techniques and discussed with respect to the amount of organofunctional groups in the materials. For comparison purposes, both an ordered MCM-41 type mesoporous silica and two silica gels of different pore size have been grafted with TMTMAC. The ion-exchange capabilities were first evaluated from batch experiments (determination of anion-exchange capacities) and then by ion-exchange voltammetry at carbon paste electrodes modified with these hybrid materials. Effective concentration of Fe(CN)(6)(3)(-) species in the anion exchangers was pointed out, while no significant accumulation of Ru(NH(3))(6)(3+) was observed. The preconcentration efficiency was discussed on the basis of the organic group content in the materials as well as their structure and porosity. A second series of materials displaying zwitterionic surfaces was finally prepared and characterized with respect to their physicochemical properties and ion-exchange voltammetric behavior. They consisted of sulfonic acid-functionalized mesoporous silica samples resulting from the oxidation of thiol-functionalized silica spheres obtained by co-condensation of mercaptopropyl-trimethoxysilane (MPTMS) and TEOS, which were then grafted with TMTMAC at various functionalization levels. Possible interactions between the ammonium and sulfonate moieties in the confined medium were pointed out from X-ray photoelectron spectroscopy. The competitive accumulation-rejection of Fe(CN)(6)(3)(-) and Ru(NH(3))(6)(3+) redox probes was finally studied by cyclic voltammetry.

Sulfonic Acid-Functionalized Mesoporous Silica: Synthesis, Characterization, and Catalytic Reaction of Alcohol Coupling to Ethers

A propanesulfonic acid-derivatized mesoporous SBA-15 catalyst was synthesized, characterized in terms of surface properties, and shown to have high selectivities for alcohol coupling to form ethers, specifically from methanol and isobutanol coupling to form methyl isobutyl ether with no detectable formation of butenes at temperatures <400 K. Kinetic analysis was consistent with competitive adsorption of the two alcohols onto Bronsted acid sites, with isobutanol being more strongly adsorbed on the acid sites than the methanol.